In the first part of this article, we talked about how GMAT quant problems are often written to imply a certain approach or solution path that is not actually the best way to do the problem. We want to reorient our view in order to pick an easier, more efficient setup or solution (if at all possible).
We finished off with a homework assignment; here’s the problem I gave you (from the free problems that come with the GMATPrep software):
* ” If , then =
“(E) 5/2 ”
The answers are fractions but they aren’t horrible fractions. They give me a value for x / y. The question is kind of annoying though, because the form doesn’t match x / y.
Or does it? Is there any way for me to rearrange that thing to make it look more like x / y?
Yes! Check it out:
Now, how did I know to do that? I’ve actually seen another problem with the same shortcut: split the numerator into two fractions. The first time I saw that other problem, though, the way I figured it out was that whole “Well, this is annoying, why did they give it to me that way!” And so I started looking at it differently and asking myself some questions:
“They gave me a value for x / y. But the question doesn’t give me x / y. Is there any way I can make x / y? There is an x on top and a y on the bottom; what if I put those two together?
“Oh, yeah, I see! It’s totally legal to split the numerator and get two separate fractions, so that would give me x / y for one of the fractions. Does that make my life any easier, though?
“The other fraction just turns into 1! That’s fantastic! I know what I’m doing now.”
Et voilà ! I know that , so . Plug that in and get 1 – 1.5 = -0.5.
Note that it’s easier to add and subtract in decimal (or percent) form, so if fractions can be converted easily (as 3/2 can), then consider doing the subtraction in decimal form. You already know that it will be easy to convert back into the final answer because look at the answer options—they’re all easy fractions to convert.
The correct answer is (A).
Quick! Glance at the answer choices for the above problem. If you did no work at all and had 1 second to make a guess, which answer would you NOT pick? Continue Reading…